# Lesson 20

A Trip to the Zoo

## Warm-up: Number Talk: Using $10 + \boxed{\phantom{4}}$ (10 minutes)

### Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for adding within 20.

Students may have many ideas for adding these numbers. In the synthesis, students discuss what they notice about the first two expressions. Students may notice that the expressions are equal and that one expression might help them with the other.

### Launch

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

### Activity

• Keep expressions and work displayed.
• Repeat with each expression.

### Student Facing

Find the value of each expression mentally.

• $$8 + 2 + 4$$
• $$8 + 6$$
• $$7 + 3 + 6$$
• $$7 + 9$$

### Student Response

For access, consult one of our IM Certified Partners.

### Activity Synthesis

• “What do you notice about the first two expressions?” (They are both 14. If 6 was broken into 2 and 4, it would be the same expression.)

## Activity 1: How Many Reptiles? (15 minutes)

### Narrative

The purpose of this activity is for students to discuss different ways to solve a three-addend story problem in which none of the addends can be combined to make 10 without being decomposed. Students solve the problem in a way that makes sense to them. Some students may build each number separately on the 10-frames and see both are filled. Some students may manipulate the numbers and think $$8 + 7 + 5 = 8 + 2 + 5 + 5$$. Different methods for solving are highlighted in the synthesis. It is important that the teacher represents student thinking, so that these methods are visible to all.

When students make sense of the story problems and connect the quantities in the story to an equation, they reason abstractly and quantitatively (MP2).

MLR6 Three Reads. Keep books or devices closed. To launch this activity, display only the problem stem, without revealing the question. “We are going to read this story problem 3 times.” After the 1st Read: “Tell your partner what happened in the story.” After the 2nd Read: “What are all the things we can count in this story?” Reveal the question. After the 3rd Read: “What are different ways we can solve this problem?”

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.

### Activity

• 4 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for students who:
• place 8, 7, and 5 counters on the 10-frames and see that they are both full
• count on
• represent the problem as $$8 + 2 + 5 + 5$$
• use a known sum like $$8 + 8$$ and then add 4 more.

### Student Facing

Jada went to the zoo with her family.
They went to the reptile exhibit and saw 8 snakes, 7 iguanas, and 5 frogs.

How many reptiles did Jada's family see?
Show your thinking using drawings, numbers, or words.

### Student Response

For access, consult one of our IM Certified Partners.

### Activity Synthesis

• Invite previously identified students to share.
• “What did they do to find the sum?”
• Record each method with an equation.

## Activity 2: Zoo Exhibits (20 minutes)

### Narrative

In this activity students solve three-addend story problems within 20. Students use methods and representations that make sense to them. When students connect the quantities in the story to an equation, they reason abstractly and quantitatively (MP2). They think strategically and may either choose to use a double 10-frame or decompose and compose the numbers in a way that helps them see the sum as 10 and some ones (MP1, MP5).

Action and Expression: Internalize Executive Functions. Invite students to plan a method, including the tools they will use, for solving story problems with three addends. If time allows, invite students to share their plan with a partner before they begin.
Supports accessibility for: Organization, Attention

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.
• “We are going to solve some problems using the different methods we’ve been working on.”

### Activity

• 6–8 minutes: independent work time
• 4 minutes: partner discussion

### Student Facing

1. In the bird exhibit, Jada saw 3 herons, 6 hawks, and 7 hummingbirds.
How many birds did Jada see?
Show your thinking using drawings, numbers, or words.

2. Next Jada went to the large cat exhibit.
There were 8 lions, 4 tigers, and 3 cheetahs.
How many large cats were there?
Show your thinking using drawings, numbers, or words.

3. Finally, Jada went to the petting zoo.
She petted 8 goats, 7 sheep, and 4 pigs.
How many animals did Jada pet?
Show your thinking using drawings, numbers, or words.

### Student Response

For access, consult one of our IM Certified Partners.

### Activity Synthesis

• Invite students to share their method for each problem.
• Record each method with an equation.

## Lesson Synthesis

### Lesson Synthesis

“In this section, we worked on different ways to add within 20. What are you most proud of? What do you still need to practice?”

## Cool-down: A Visit with the Primates (5 minutes)

### Cool-Down

For access, consult one of our IM Certified Partners.

## Student Section Summary

### Student Facing

We saw that making a ten could help when we add 3 numbers together.

$$4 + 8 + 6 = 10 + 8 = 18$$

We saw that making a ten could also help when we add 2 numbers together.

$$4 + 8 = 4 + 6 + 2 = 10 + 2 = 12$$